Project on Concrete Mix Design for various grades of Concrete

Concrete Mix Design for M35 grade concrete with fly ash 

1. Stipulation for proportioning

1. Grade of concrete : M35
2. Types of Cement : OPC 43 grade conforming to IS 8112
3. Types of mineral admixtures: Fly ash conforming to IS 3812 (Part 1)
4. Maximum sieve size of aggregate: 20mm
5. Mininmum cement content: 320kg/m^3  (fram Table 5 of IS 456 2000, exposure condition)
6. Maximum w/c ratio : 0.45
7. Workability :100 mm (Slump value for pumpable concrete)
8. Exposure condition : Severe (for Reinforced concrete)
9. Method of concrete placing : Pumping
10. Degree of supervision : Good
11. Type of aggregate : Crushed angular aggregate
12. Maximum cement content : 450kg/m^3
13.  Chemical admixture type: Superplasticizer

    II. Test data for material

1. Cement used : OPC 43 grade conforming to IS 8112
2. Specific gravity of cement : 3.12
3. Fly ash : conforming to IS 3812 (Part 1)
4. Specific gravity of fly ash : 2.2
5. Chemical admixtures : Superplasticizer conforming to IS 9103
6. Specific gravity of coarse aggregate : 2.74
7. Specific gravity of fine aggregate : 2.74
8. Water absorption of coarse aggregate : 0.5%
9. Water absorption of fine aggregate : 1%
10. Free surface moisture of coarse aggregate : NIL
11. Free surface moisture of fine aggregate : NIL
12. Sieve analysis

Coarse aggregate

IS sieve size         (mm)

Analysis of Coarse       aggregate fraction

% of different fraction

Remarks

	I	II	I	II	Combined
			60%	40%		Conforming to Table 2 of IS 383
20	100	100	60	40	100
10	0	71.2	0	28.5	28.5
4.75		9.4		3.7	3.7
2.36		0

Fine aggregate to grading zone I of table 4 of IS 383

    III. Target strength of mix proportion

                       f'ck = fck +1.65 S

  From Table 1 of IS 10262 :2009, standard deviation =s = 5 N/mm^2

  Therefore, target strength = 35 +1.65 S 

                                         = 35 + 1.65 X 5

                                         = 43.25 N/mm^2

     IV. Selection of w/c ratio 

From Table 5 of IS 456 2000 for severe exposure, Maximum water-cement ratio = 0.45.

Based on experience, adopt w/c ratio as 0.40

Therfore,  0.40 < 0.45................................................Hence, Ok

    V.  Selection of water cement content

From Table 2 of IS 456, maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197 lit

As, super plasticizer is used, the water content can be reduced upto 30%

BAsed on trials, water content reduction of 25% is acheived with plasticizer.

Hence, arrived water content = 197-[197 x (25/100)]

                                           = 147 litres.

    VI. Calculation of cement content

Water-cement ratio =0.45

Cement content = 147/0.45 = 350 kg/m³ 

From Table 5 of IS 456, minimum cement content for ‘Very Severe‘ exposure condition = 340 kg/m³ 

350 kg/m³ > 340 kg/m³, hence, O.K.

Now, to proportion of mix containing fly ash the following steps are suggested

1.  Percentage of fly ash needs to be added based on project requirement and quality of materials.
2.  In some cases increase in cementious material can be warented.Increase in cementious material content and its percentage may be based on experience and trials (This eg. is with increase of 10% cementious material content)

cementious material content = 350 X 1.1 

                                          = 385 kg/m^3

water content  = 140 Kg/m^3

So, w/c ratio = 140 / 385  =0.364

Fly ash @30% total cementious material content = 385 X 30% = 115 kg/m^3

Cement(OPC) = 385-115 =270 kg/m^3

Saving cement while using fly ash = 350 -270 =80 kg/m^3 and fly ash being utilised = 115 kg/m^3

   VII. Proportion of the Volume of Coarse Aggregate and Fine Aggregate Content 

From Table 3 of IS 10262, volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 = 0.62.

 In the present case, the water-cement ratio is 0.45. Therefore, the volume of coarse aggregate is required to be increased to reduce the fine aggregate content.

As the water-cement ratio is lower by 0.10, the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio). Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.45 = 0.63.

NOTE – In case the coarse aggregate is not angular one. then also the volume of coarse aggregate may be required 10 be increased suitably, based on experience. 

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.63 x 0.9 = 0.567.

 Volume of fine aggregate content =1 – 0.567 =0.433

   VIII. Mix Calculations

1. Volume of concrete = 1m^3

2. Volume of cement = (Mass of cement/Specific Gravity of Cement) X (1/1000)

                              = (350/3.12) X (1/1000) 

                              = 0.112 m^3

3. Volume of fly ash = (Mass of fly ash/Specific Gravity of fly ash) X (1/1000)

                                  =(115/2.2) X (1/1000)

1. Volume of water = (Mass of water/specific gravity of water) X (1/1000)

                           = (147/1) X (1/1000)

                           = 0.147 m^3

2. Volume of superplasticizer = (Mass of superplasticizer / Specific gravity of admixture) X (1/1000)

                                         = (7/1.145) X (1/1000)

                                         = 0.006 m^3

3. Volume of all aggregate = (a-(b+c+d))

                                      = 1 – (0.112 + 0.147+0.006)

                                      = 0.735 m^3

4. Mass of coarse aggregate = Volume of all aggregate X volume of coarse aggregate X Specific gravity of                                           coarse aggregate X 1000

                                         = 0.735 x 0.567 x 2.74 x 1000

                                          = 1141.88 kg

5. Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine                                         aggregate X 1000

                                      = 0.735 x 0.433 x 2.56 x 1000

                                      = 814.73 kg

    IX. Concrete Mix Proportions 

• Cement = 350 kg/m³
• Water = 147 kg/m³
• Super plasticizer = 7 kg/m³
• Fine aggregates = 814.73 kg/m³
• Coarse aggregate = 1141.88 kg/m³
• W/c = 0.45

The Mix Ratio of M35 as obtained is 1 : 2.32 : 3.26 (Cement : Fine aggregate : Coarse aggregate)

This is the procedure for mx design calculation of M35 grade concrete.

Concrete Mix Design for M50 grade concrete

    I. Stipulations for Concrete Mix Design

• Grade designation : M 50
• Type of cement : OPC 53 grade confirming to IS 8112
• Maximum nominal size of aggregate : 20 mm
• Minimum cement content : 360 kg/m^3
• Maximum water-cement ratio : 0.35
• Workability : 50-75 mm (slump)
• Exposure condition : Extreme (for reinforced concrete)
• Method of concrete placing : Pumping
• Degree of supervision : Good
• Type of aggregate : Crushed angular aggregate
• Maximum cement content : 450 kg/m^3
• Chemical admixture type : Super Plasticizer

    II. Test Data for Materials

The following data are collected by performing standard tests in a laboratory.

Specific gravity of cement : 3.12

Specific gravity of Coarse Aggregate : 2.74

Specific gravity of Fine Aggregate : 2.56

   III. Procedure for Concrete Mix Design of M 50 Concrete

1.  Target Strength for Mix Proportioning 

f_target = f_ck + 1.65 x s

f_target denotes the Target Average Compressive Strength at 28 days,

 f_ck denotes the Characteristic Compressive Strength at 28 days,

‘s’ stands for Standard Deviation 

According to the table 1 of IS 10262 2009,

standard deviation, s = 5.0 N/mm^2

Therefore, target strength = 50 + 1.65 x 5.0 = 58.25 N/mm^2

    IV. Selection of Water/Cement Ratio

From Table 5 of IS 456 2000

Maximum water-cement ratio = 0.35 

     V. Selection of Water Content 

From Table 2 of IS 456 maximum water content =186 litres (for 25 to 50 mm slump range) for 20 mm aggregate.

Estimated water content for 100 mm slump =186+(6/100) x 186 =197 litres.

(Note: If Super plasticizer is used, the water content can be reduced up to 20% and above.)

Based on trials with Super plasticizer water content reduction of 27% has been achieved, Hence the arrived water content = 197 – [197 x (27/100)] = 143 litres.

     VI. Calculation of Cement Content

Water-cement ratio = 0.35

Cement content = 143/0.35 = 410 kg/m^3 

From Table 5 of IS 456 minimum cement content for ‘Extreme exposure’ condition = 360 kg/m^3 

410 kg/m^3  > 360 kg/m^3 , hence, O.K.

     VII. Proportion of Volume of Coarse Aggregate and Fine Aggregate Content 

From Table 3 of IS 10262 volume of coarse aggregate corresponding to 20 mm size aggregate and fine aggregate (Zone II) for a water-cement ratio of 0.50 =0.62.

 In the present case, the water-cement ratio is 0.35. Therefore. the volume of coarse aggregate is required to be increased to decrease the fine aggregate content. As the water-cement ratio is lower by 0.10. the proportion of the volume of coarse aggregate is increased by 0.02 (at the rate of -/+ 0.01 for every ± 0.05 change in the water-cement ratio).

Therefore. the corrected proportion of the volume of coarse aggregate for the water-cement ratio of 0.35 = 0.65.

NOTE – In case the coarse aggregate is not angular one, then the volume of coarse aggregate may be increased by 10 percent based on experience. 

For pumpable concrete, these values should be reduced by 10 percent.

Therefore, volume of coarse aggregate = 0.65 x 0.9 = 0.585.

Volume of fine aggregate content =1 – 0.585 =0.415

    VIII. Mix Calculations

• Volume of concrete = 1m^3

• Volume of cement = (Mass of Cement/ Its Specific Gravity ) X (1/1000)

                             = (410/3.12) X (1/1000) 

                             = 0.131 m^3

• Volume of Water = (Mass of water/specific gravity of water) X (1/1000)

                           = (143/1) X (1/1000)

                           = 0.143 m^3

• Volume of Superplasticizer = (Mass of Superplasticizer / Specific gravity of admixture) X (1/1000)

                                         = (8.2/1.145) X (1/1000)

                                         = 0.007 m^3

• Volume of all aggregate = (a – (b + c + d))

                                           = 1 – (0.131 + 0.143+0.007)

                                           = 0.719 m^3

• Mass of coarse aggregate = Volume of All Aggregate X Volume of Coarse Aggregate X Specific Gravity                                             of Coarse Aggregate X 100

                                       = 0.719 x 0.585 x 2.74 x 1000

                                       = 1152.48 kg

• Mass of fine aggregate = Volume of all aggregate X volume of fine aggregate X Specific gravity of fine                                         aggregate X 1000

                                         = 0.719 x 0.415 x 2.56 x 1000

                                         = 763.86 kg

    IX. Concrete Mix Proportions 

• Cement = 410 kg/m³
• Water = 143 kg/m³
• Super plasticizer = 7 kg/m³
• Fine aggregates = 763.86 kg/m³
• Coarse aggregate = 1152.48 kg/m³
• W/c = 0.35

Trial mix ration = 1:1.86:2.81